1. Field of the Invention
The present invention relates to a technique of realizing satisfactory image stabilization in a lens-interchangeable image capture apparatus capable of movie shooting.
2. Description of the Related Art
Recently, not only still cameras but also video cameras of a lens-interchangeable type have been commercialized. Along with popularization of large-screen televisions and improvement of the video quality, these products have received attention as a means for obtaining a video the user expects. As a lens to be used, these products are designed to use, for example, an interchangeable lens for a single-lens reflex camera. The user can apply the property he always has. The image stabilization performance of image capture devices such as a video camera is improving year by year, and even a large blur generated when the user walks or runs can be corrected on the wide angle side of the lens.
Considering the image stabilization performance of a lens-interchangeable camera system, when an image stabilization shift lens arranged in the lens is greatly moved to correct a large blur during walking or the like on the wide angle side, some optical performances such as the peripheral brightness and MTF may be impaired. To stop a large blur during walking in this system, electronic correction needs to be performed in the camera. A large blur is corrected using extra pixels of an image sensor mounted in the camera for image stabilization.
As this image sensor, a CMOS sensor is often used nowadays. This is because the CMOS sensor has higher sensitivity, smaller power consumption, and lower cost, compared to a CCD sensor, and can read out data of each pixel at random. However, when electronic correction is performed by the CMOS sensor, a wobbling image distortion occurs under the influence of a rolling shutter distortion, causing an adverse effect such that the user who views the movie feels motion sickness.
As a method of correcting the rolling shutter distortion, Japanese Patent No. 3925415 discloses a method of correcting a rolling shutter distortion by using a gyro sensor output. Japanese Patent No. 4340915 discloses a method of detecting a motion vector from a captured video and correcting a rolling shutter distortion by using the detection result. By correcting the rolling shutter distortion, even an image capture apparatus which incorporates a CMOS sensor and performs electronic correction for a camera shake can achieve satisfactory image stabilization.
However, the rolling shutter distortion correction using motion vector detection has problems such as a correction error arising from a motion vector detection error, and a long processing time. It is therefore difficult to use this correction in movie processing directly. When distortion correction is performed using a gyro signal, an output from a gyro sensor arranged in the lens or camera is used. In a camera system in which an optical image stabilization mechanism is mounted in a lens, an image formed on the CMOS sensor is an image having undergone optical axis correction by the image stabilization mechanism. That is, the correlation between a gyro output and a formed video is lost. For this reason, if a rolling shutter distortion is corrected simply using only a gyro output, the influence of the distortion is not completely removed, or over-correction is executed, leaving a wobbling image.